With increased demand for and variety of the Internet services, communication traffic transmitted in a backbone network continues to increase remarkably. To cope with this trend, a backbone network having larger capacity with higher transmission speed is being constructed based on new technologies such as the wavelength division multiplexing (WDM).
Also, the development of an optical cross-connect (OXC) and an optical add-drop multiplexer (OADM) is currently in progress aiming at efficient operation of a mesh network employing flexible control with shared spare (protection) wavelengths. Through these technologies, the implementation of new communication infrastructure and new services is expected.
In a large-scale WDM network, communication damages caused by a failure is increasing as services provided by a system increases. In order to improve the system reliability, development of an advanced network management system becomes a key issue. A technology for prompt service restoration in an optical layer when a link or node fails is important among others.
The inventors of the present invention have been studying a pre-plan type failure restoration system which enables prompt service restoration when a WDM network fails. (Reference: FUJII, Y., MIYAZAKI, K., and ISEDA, K.: “A study on a pre-plan type failure restoration system”, Technical Report of the Institute of Electronics, Information and Communication Engineers (IEICE), TM2000-60, Nov. 2000, pp. 67–72.)
In such a pre-plan type failure restoration system, failure information originated from a node having detected a failure is transferred to a neighboring node then successively to a next neighboring node (‘flooding’) in which predetermined protecting route information is preset. Each node switches over a route in parallel according to the preset protecting route information, enabling to shorten a time for the dynamic protecting route search. Thus prompt service restoration is realized.
However, even a parallel route switchover is possible, it may still be a problem if substantially long time is consumed before each node along the protecting route receives the failure information.
In addition, when designing a pre-determined protecting route, conventional methods mainly aim to minimize the number of total spare wavelengths (resources) only.